Integrated low noise amplifier

0001This patent application is claiming priority under 35 USC § 120 as a continuation patent application to patent application entitled AN INTEGRATED CIRCUIT LOW NOISE AMPLIFIER AND APPLICATIONS THEREOF, having a Ser. No. of 10/128,193, and a filing date of Apr. 23, 2002, which is now issued as U.S. Pat. No. 6,809,581.

TECHNICAL FIELD OF THE INVENTION

0002This invention relates generally to communication systems and more particularly to radio receivers used within such communication systems.

BACKGROUND OF THE INVENTION

0003Communication systems are known to support wireless and wire lined communications between wireless and/or wire lined communication devices. Such communication systems range from national and/or international cellular telephone systems to the Internet to point-to-point in-home wireless networks. Each type of communication system is constructed, and hence operates, in accordance with one or more communication standards. For instance, wireless communication systems may operate in accordance with one or more standards including, but not limited to, IEEE 802.11, Bluetooth, advanced mobile phone services (AMPS), digital AMPS, global system for mobile communications (GSM), code division multiple access (CDMA), local multi-point distribution systems (LMDS), multi-channel-multi-point distribution systems (MMDS), and/or variations thereof.

0004Depending on the type of wireless communication system, a wireless communication device, such as a cellular telephone, two-way radio, personal digital assistant (PDA), personal computer (PC), laptop computer, home entertainment equipment, et cetera communicates directly or indirectly with other wireless communication devices. For direct communications (also known as point-to-point communications), the participating wireless communication devices tune their receivers and transmitters to the same channel or multiple channels (e.g., one or more of the plurality of radio frequency (RF) carriers of the wireless communication system) and communicate over that channel. For indirect wireless communications, each wireless communication device communicates directly with an associated base station (e.g., for cellular services) and/or an associated access point (e.g., for an in-home or in-building wireless network) via an assigned channel, or channels. To complete a communication connection between the wireless communication devices, the associated base stations and/or associated access points communicate with each other directly, via a system controller, via the public switch telephone network, via the internet, and/or via some other wide area network.

0005For each wireless communication device to participate in wireless communications, it includes a built-in radio transceiver (i.e., receiver and transmitter) or is coupled to an associated radio transceiver (e.g., a station for in-home and/or in-building wireless communication networks, RF modem, etc.). As is known, the receiver receives RF signals, demodulates the RF carrier frequency from the RF signals via one or more intermediate frequency stages to produce baseband signals, and demodulates the baseband signals in accordance with a particular wireless communication standard to recapture the transmitted data. The transmitter converts data into RF signals by modulating the data in accordance with the particular wireless communication standard to produce baseband signals and mixes the baseband signals with an RF carrier in one or more intermediate frequency stages to produce RF signals.

0006To recapture data from RF signals, a receiver includes a low noise amplifier, down conversion module and demodulation module. For radio frequency integrated circuits, it is desirable to provide the low noise amplifier with differential RF signals instead of single ended RF signals to improve noise performance and common mode rejection. To convert received single ended RF signals into differential RF signals, a receiver includes a balun (i.e., a balanced/unbalanced transformer).

0007Until very recently, the baluns were off-chip, i.e., on the printed circuit board, and were typically implemented in the form of micro-strip lines. Recent attempts to integrate a balun onto a radio frequency integrated circuit have had limited success. For example, parallel winding, inter-wound winding, overlay winding, single planar, square wave winding, and concentrical spiral winding on-chip baluns have been tried with limited success. Each of these on-chip baluns suffers from one or more of: low quality factor, (which causes the balun to have a relatively large noise figure); too low of a coupling coefficient (which results in the inductance value of the balun not significantly dominating the parasitic capacitance making impedance matching more complex); asymmetrical geometry (which results in degradation of differential signals); and a relatively high impedance ground connection at the operating frequency.

0008Therefore, a need exists for an integrated low noise amplifier that includes a symmetrical balun that has a low noise figure, low ground impedance at the operating frequency and has an inductance value that is dominant at the operating frequency.

SUMMARY OF THE INVENTION

0009The integrated circuit low noise amplifier disclosed herein substantially meets these needs and others. In one embodiment, an integrated circuit (IC) low noise amplifier includes an on-chip balun and an on-chip differential amplifier. The on-chip balun is operably coupled to convert a single-ended signal into a differential signal. The on-chip differential amplifier is operably coupled to amplify the differential signal.

0010In another embodiment, an integrated circuit (IC) radio receiver includes a low noise amplifier, a down conversion module, and a filtering module. The low noise amplifier is operably coupled to amplify a radio frequency (RF) signal to produce an amplified RF signal. The down conversion module is operably coupled to convert the amplified RF signal into a baseband signal. The filtering module is operably coupled to filter the baseband signal. The low noise amplifier includes an on-chip balun operably coupled to convert a single-ended signal into a differential signal and an on-chip differential amplifier operably coupled to amplify the differential signal.

BRIEF DESCRIPTION OF THE DRAWINGS

<figref idref="DRAWINGS">FIG. 1</figref> illustrates a schematic block diagram of a wireless communication system in accordance with the present invention;

<figref idref="DRAWINGS">FIG. 2</figref> illustrates a schematic block diagram of a wireless communication device in accordance with the present invention;

<figref idref="DRAWINGS">FIG. 3</figref> illustrates a schematic block diagram of an integrated low noise amplifier in accordance with the present invention;

<figref idref="DRAWINGS">FIG. 4</figref> illustrates a schematic block diagram of a line impedance matching circuit and on-chip balun in accordance with the present invention; and

<figref idref="DRAWINGS">FIG. 5</figref> illustrates an alternate embodiment of an integrated circuit low noise amplifier in accordance with the present invention.

DETAIL DESCRIPTION OF A PREFERRED EMBODIMENT

0016<figref idref="DRAWINGS">FIG. 1</figref> illustrates a schematic block diagram of a communication system <b>10</b> that includes a plurality of base stations and/or access points <b>12</b>–<b>16</b>, a plurality of wireless communication devices <b>18</b>–<b>32</b> and a network hardware component <b>34</b>. The wireless communication devices <b>18</b>–<b>32</b> may be laptop host computers <b>18</b> and <b>26</b>, personal digital assistant hosts <b>20</b> and <b>30</b>, personal computer hosts <b>24</b> and <b>32</b> and/or cellular telephone hosts <b>22</b> and <b>28</b>. The details of the wireless communication devices will be described in greater detail with reference to <figref idref="DRAWINGS">FIG. 2</figref>.

0017The base stations or access points <b>12</b> are operably coupled to the network hardware <b>34</b> via local area network connections <b>36</b>, <b>38</b> and <b>40</b>. The network hardware <b>34</b>, which may be a router, switch, bridge, modem, system controller, et cetera provides a wide area network connection <b>42</b> for the communication system <b>10</b>. Each of the base stations or access points <b>12</b>–<b>16</b> has an associated antenna or antenna array to communicate with the wireless communication devices in its area. Typically, the wireless communication devices register with a particular base station or access point <b>12</b>–<b>14</b> to receive services from the communication system <b>10</b>. For direct connections (i.e., point-to-point communications), wireless communication devices communicate directly via an allocated channel.

0018Typically, base stations are used for cellular telephone systems and like-type systems, while access points are used for in-home or in-building wireless networks. Regardless of the particular type of communication system, each wireless communication device includes a built-in radio and/or is coupled to a radio. The radio includes an integrated low noise amplifier as disclosed herein to enhance performance of radio frequency integrated circuits.

0019<figref idref="DRAWINGS">FIG. 2</figref> illustrates a schematic block diagram of a wireless communication device that includes the host device <b>18</b>–<b>32</b> and an associated radio <b>60</b>. For cellular telephone hosts, the radio <b>60</b> is a built-in component. For personal digital assistants hosts, laptop hosts, and/or personal computer hosts, the radio <b>60</b> may be built-in or an externally coupled component.

0020As illustrated, the host device <b>18</b>–<b>32</b> includes a processing module <b>50</b>, memory <b>52</b>, radio interface <b>54</b>, input interface <b>58</b> and output interface <b>56</b>. The processing module <b>50</b> and memory <b>52</b> execute the corresponding instructions that are typically done by the host device. For example, for a cellular telephone host device, the processing module <b>50</b> performs the corresponding communication functions in accordance with a particular cellular telephone standard.

0021The radio interface <b>54</b> allows data to be received from and sent to the radio <b>60</b>. For data received from the radio <b>60</b> (e.g., inbound data), the radio interface <b>54</b> provides the data to the processing module <b>50</b> for further processing and/or routing to the output interface <b>56</b>. The output interface <b>56</b> provides connectivity to an output display device such as a display, monitor, speakers, et cetera such that the received data may be displayed. The radio interface <b>54</b> also provides outbound data from the processing module <b>50</b> to the radio <b>60</b>. The processing module <b>50</b> may receive the outbound data from an input device such as a keyboard, keypad, microphone, et cetera via the input interface <b>58</b> or generate the data itself. For data received via the input interface <b>58</b>, the processing module <b>50</b> may perform a corresponding host function on the data and/or route it to the radio <b>60</b> via the radio interface <b>54</b>.

0022Radio <b>60</b> includes a host interface <b>62</b>, a receiver section, a transmitter section, local oscillation module <b>74</b>, an antenna switch <b>73</b>, and an antenna <b>86</b>. The receiver section includes a digital receiver processing module <b>64</b>, analog-to-digital converter <b>66</b>, filtering/gain module <b>68</b>, down conversion module <b>70</b>, receiver filter module <b>71</b>, low noise amplifier <b>72</b>, and at least a portion of memory <b>75</b>. The transmitter section includes a digital transmitter processing module <b>76</b>, digital-to-analog converter <b>78</b>, filtering/gain module <b>80</b>, up-conversion module <b>82</b>, power amplifier <b>84</b>, transmitter filter module <b>85</b>, and at least a portion of memory <b>75</b>. The antenna <b>86</b> may be a single antenna that is shared by the transmit and receive paths via the antenna switch <b>73</b> or may include separate antennas for the transmit path and receive path and omit the antenna switch. The antenna implementation will depend on the particular standard to which the wireless communication device is compliant.

0023The digital receiver processing module <b>64</b> and the digital transmitter processing module <b>76</b>, in combination with operational instructions stored in memory <b>75</b>, execute digital receiver functions and digital transmitter functions, respectively. The digital receiver functions include, but are not limited to, digital intermediate frequency to baseband conversion, demodulation, constellation demapping, decoding, and/or descrambling. The digital transmitter functions include, but are not limited to, scrambling, encoding, constellation mapping, modulation, and/or digital baseband to IF conversion. The digital receiver and transmitter processing modules <b>64</b> and <b>76</b> may be implemented using a shared processing device, individual processing devices, or a plurality of processing devices. Such a processing device may be a microprocessor, micro-controller, digital signal processor, microcomputer, central processing unit, field programmable gate array, programmable logic device, state machine, logic circuitry, analog circuitry, digital circuitry, and/or any device that manipulates signals (analog and/or digital) based on operational instructions. The memory <b>75</b> may be a single memory device or a plurality of memory devices. Such a memory device may be a read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, and/or any device that stores digital information. Note that when the processing module <b>64</b> and/or <b>76</b> implements one or more of its functions via a state machine, analog circuitry, digital circuitry, and/or logic circuitry, the memory storing the corresponding operational instructions is embedded with the circuitry comprising the state machine, analog circuitry, digital circuitry, and/or logic circuitry.

0024In operation, the radio <b>60</b> receives outbound data <b>94</b> from the host device via the host interface <b>62</b>. The host interface <b>62</b> routes the outbound data <b>94</b> to the digital transmitter processing module <b>76</b>, which processes the outbound data <b>94</b> in accordance with a particular wireless communication standard (e.g., IEEE 802.11a, IEEE 802.11b, Bluetooth, et cetera) to produce digital transmission formatted data <b>96</b>. The digital transmission formatted data <b>96</b> will be a digital base-band signal or a digital low IF signal, where the low IF will be in the frequency range of zero to a few megahertz.

0025The digital-to-analog converter <b>78</b> converts the digital transmission formatted data <b>96</b> from the digital domain to the analog domain. The filtering/gain module <b>80</b> filters and/or adjusts the gain of the analog signal prior to providing it to the up-conversion module <b>82</b>. The up-conversion module <b>82</b> directly converts the analog baseband or low IF signal into an RF signal based on a transmitter local oscillation provided by local oscillation module <b>74</b>. The power amplifier <b>84</b> amplifies the RF signal to produce outbound RF signal <b>98</b>. The antenna <b>86</b> transmits the outbound RF signal <b>98</b> to a targeted device such as a base station, an access point and/or another wireless communication device.

0026The radio <b>60</b> also receives an inbound RF signal <b>88</b> via the antenna <b>86</b>, which was transmitted by a base station, an access point, or another wireless communication device. The antenna <b>86</b> provides the inbound RF signal <b>88</b> to the low noise amplifier <b>72</b>, which amplifies the signal <b>88</b> in accordance with the teachings of the present invention, which will be described in greater detail with reference to <figref idref="DRAWINGS">FIGS. 3–5</figref>, to produce an amplified inbound RF signal. The low noise amplifier <b>72</b> provide the amplified inbound RF signal to the down conversion module <b>70</b>, which directly converts the amplified inbound RF signal into an inbound low IF signal based on a receiver local oscillation provided by local oscillation module <b>74</b>. The down conversion module <b>70</b> provides the inbound low IF signal to the filtering/gain module <b>68</b>, which filters and/or adjusts the gain of the signal before providing it to the analog to digital converter <b>66</b>.

0027The analog-to-digital converter <b>66</b> converts the filtered inbound low IF signal from the analog domain to the digital domain to produce digital reception formatted data <b>90</b>. The digital receiver processing module <b>64</b> decodes, descrambles, demaps, and/or demodulates the digital reception formatted data <b>90</b> to recapture inbound data <b>92</b> in accordance with the particular wireless communication standard being implemented by radio <b>60</b>. The host interface <b>62</b> provides the recaptured inbound data <b>92</b> to the host device <b>18</b>–<b>32</b> via the radio interface <b>54</b>.

0028As one of average skill in the art will appreciate, the radio may be implemented a variety of ways to receive RF signals and to transmit RF signals and may be implemented using a single integrated circuit or multiple integrated circuits. Further, at least some of the modules of the radio <b>60</b> may be implemented on the same integrated circuit with at least some of the modules of the host device <b>18</b>–<b>32</b>. Regardless of how the radio is implemented, the concepts of the present invention are applicable.

0029<figref idref="DRAWINGS">FIG. 3</figref> illustrates a schematic block diagram of an integrated circuit low noise amplifier <b>72</b> that includes a line impedance matching circuit <b>100</b>, an on-chip balun <b>102</b>, and an on-chip differential amplifier <b>104</b>. The line impedance matching circuit <b>100</b>, which will be described in greater detail with reference to <figref idref="DRAWINGS">FIG. 4</figref>, receives a single ended signal <b>106</b> (e.g., a singled ended RF signal <b>88</b>) via an input line <b>108</b> from the antenna. The line impedance matching circuit <b>100</b> provides an impedance, in conjunction with the primary winding of the balun <b>102</b>, to substantially match the impedance of the antenna at the operating frequency, or frequencies, of the antenna. Typically, an antenna will have a 50 OHM impedance at the operating frequencies. Correspondingly, the line impedance matching circuit <b>100</b> in conjunction with the primary of the on-chip balun <b>102</b> will have an impedance of approximately 50 OHMS at the same frequencies.

0030The on-chip balun <b>102</b>, which may be a symmetrical on-chip balun as described in co-pending patent application BP 2095 entitled ON-CHIP TRANSFORMER BALUN, having a filing date of Jan. 23, 2002, and a Ser. No. of 10/055,425. The primary winding of the on-chip balun is operably coupled to the line impedance matching circuit <b>100</b> to receive the single ended signal <b>106</b>. The secondary is center tapped to produce a differential signal <b>110</b> from the single ended signal <b>106</b>. The center tap connection is tied to one node of the primary, which in turn is coupled to the ground of the integrated circuit low noise amplifier <b>72</b>, which may be done through a ground circuit that may be in the line impedance matching circuit or a separate circuit. While the on-chip balun <b>102</b> may have a noise figure that is greater than an off-chip balun, the noise figure of the on-chip balun <b>102</b> is reduced to more than acceptable levels by providing gain within the on-chip balun <b>102</b>. For example, the on-chip balun may have a turns ratio of 2:9, where the center tap splits the nine turns of the secondary. To further improve the performance of the on-chip balun <b>102</b>, the primary may include three shunted primary windings to minimize Ohmic losses.

0031The on-chip differential amplifier <b>104</b> is operably coupled to receive the differential signal <b>110</b> via AC coupling capacitors C<b>1</b> and C<b>2</b>, which are sized to block low frequency signals and to pass high frequency signals. The on-chip differential amplifier <b>104</b> includes resistor R<b>3</b>, inductors L<b>1</b>, L<b>2</b>, L<b>3</b> and L<b>4</b>, and transistors T<b>1</b>, T<b>2</b>, T<b>3</b> and T<b>4</b>. Transistors T<b>3</b> and T<b>4</b> provide the differential input for the on-chip differential amplifier <b>104</b> and are biased in the linear region via resistors R<b>1</b> and R<b>2</b> to a low noise amplifier bias value <b>114</b>. The design of transistor T<b>3</b> in conjunction with the inductance of L<b>3</b> is tuned to provide impedance matching with the output of the on-chip balun <b>102</b>. Similarly, transistor T<b>4</b> and inductor L<b>4</b> are designed to provide impedance matching with the output of balun <b>102</b>. Further, the inductors L<b>3</b> and L<b>4</b> have a relatively low Q, while transistors T<b>3</b> and T<b>4</b> have a large transconductance (G_m) value to provide a wide frequency range of operation while maintaining a relatively constant impedance. Still further, the parasitic capacitances of transistors T<b>3</b> and T<b>4</b> are sized with respect to the inductance values of L<b>3</b> and L<b>4</b> to have an insignificant contribution to the impedance of the input of the differential amplifier <b>104</b> at the operating frequencies. Transistors T<b>1</b> and T<b>2</b> are biased via a bias voltage <b>116</b>. As configured, the on-chip differential amplifier <b>104</b> produces an amplified differential signal <b>112</b> from the differential signal <b>110</b>.

0032<figref idref="DRAWINGS">FIG. 4</figref> illustrates a schematic block diagram of the line impedance matching circuit <b>100</b> and the on-chip balun <b>102</b>. As shown, the line impedance matching circuit <b>100</b> includes capacitors C<b>3</b> and C<b>4</b> and a ground circuit <b>122</b>. The ground circuit <b>122</b> may be implemented utilizing a capacitor C<b>5</b>. The capacitors C<b>3</b> and C<b>4</b> are tuned with respect to the inductance value of the on-chip balun to provide the desired input impedance at a particular operating frequency range for the IC low noise amplifier and, in addition, to provide gain. The particular operating frequency range may be from 2.4 gigahertz plus or minus 10%, 5.2–5.75 gigahertz plus or minus 10% and/or any other operating range that is used to transceive RF signals.

0033To simplify the impedance matching to include two capacitors, the on-chip balun <b>102</b> is designed such that its impedance at the operating frequencies is primarily determined by its inductances and not its parasitic capacitance. This is achieved by providing a sufficient coupling coefficient as further described in co-pending patent application entitled ON-CHIP TRANSFORMER BALUN, having a filing date of Jan. 23, 2002, and a Ser. No. of 10/055,425. If, however, the parasitic capacitance of the on-chip balun <b>102</b> is a significant factor at the operating frequencies, the line impedance matching circuit <b>100</b> would need to account for the impedance contributions of the parasitic capacitance.

0034The ground circuit <b>122</b>, which includes capacitor C<b>5</b>, has a capacitance value such that, when coupled in series with the equivalent circuit <b>120</b> of the package and bond wire (which includes an inductor and resistor), the impedance at the operating frequencies is minimized. In particular, the capacitance value in combination with the inductance value of the bond wire and package provides a bandpass filter at the operating frequencies. As one of average skill in the art will appreciate, the ground circuit <b>122</b> may be implemented in a variety of ways to provide a low impedance path for the primary of the on-chip balun to ground.

0035<figref idref="DRAWINGS">FIG. 5</figref> illustrates an alternate schematic block diagram of an integrated circuit low noise amplifier <b>72</b>. In this embodiment, the integrated circuit low noise amplifier <b>72</b> includes an on-chip balun <b>102</b> and the differential amplifier <b>104</b>. The on-chip balun <b>102</b> may be modified to include a ground circuit such that inductance and resistance of packaging and bond wires are compensated for such that a low impedance ground path is obtained. In addition, the on-chip balun <b>102</b> may be modified to include a line impedance matching circuit that includes a pair of capacitors, one coupled in series with the single ended signal <b>102</b> and another in parallel with the primary winding of the on-chip balun to provide impedance matching.

0036The preceding discussion has presented an integrated circuit low noise amplifier and applications within a radio receiver. By incorporating an on-chip balun with a differential amplifier, an integrated circuit low noise amplifier that provides a low impedance ground path, symmetrical differential signaling, a low noise figure, substantial gain, and impedance matching is obtained. As one of average skill in the art will appreciate, other embodiments may be derived from the teaching of the present invention, without deviating from the scope of the claims.